A direct box is a device used to adapt an unbalanced AC audio signal to a balanced low impedance AC output for transmission to an audio console. A switch, commonly know as a “ground lift switch,” is provided in the direct box to connect or disconnect separate ground points between the input and the output of the direct box. The position of the switch is manually controlled by the user at the direct box. The ideal position of the switch is dependent on the types of equipment connected at both the input and output of the direct box and related grounds.
An input selection box, commonly called an A/B box, is a device used to route one of two (or more) inputs to a single common output. A switch is provided in these units to select which input is routed to the output. The position of this switch is manually controlled by the user at the A/B box.
Phantom power is a system for applying a DC voltage across the balanced AC inputs of audio consoles. Phantom power has primarily been used to power the electronics of amplifier circuits in active direct boxes or condenser microphones. Phantom power is usually configurable to be ON or OFF by a control switch on the audio console.
The method and/or apparatus described below relates to the use of such phantom power to control a direct box, an A/B box, or other apparatus.